Understanding the ‘new NBA’ — Part I
Almost 7 seasons ago, a young James Harden was revolutionizing the NBA with his frequency of 3-point shot attempts and shot attempts at the rim. Today, we all have become accustomed to the ‘new NBA’ where 30 three point attempts per game is a norm for a good team. This glamorous three point revolution was accompanied by a lot of other changes which haven’t really come to the forefront of the public eye. This two part series focuses on identifying the changes that have happened.
Focus on each possession
In 2003, Dean Oliver published Basketball on Paper. In that book, he noted that possessions are the currency of a basketball game. Oliver notes that for basketball, it’s points per possession, and not points per game, that’s important. He suggested that a team scoring 100 points in 100 possessions was better than another team that scored 102 points in 105 possessions. This is because the opposition team would also have the same number of possessions. Efficient use of each possession was the key to success in an NBA game. This gave rise to the metric ‘points per 100 possessions’, which is the holy grail for NBA analysts.
Pace
This idea also brings us to the concept of pace in a basketball game. Pace is simply the average number of possessions a team plays in a 48 minute basketball game. Image 1 shows the evolution of pace and points per 100 possessions in basketball.
Note: Free throw points are not included in this image.
As you can see, the points per possession had been rising even before the three-point revolution. One may argue that it is more accelerated now. More strikingly, pace has also seen a continual increase since the beginning of the revolution in 2012. Neither Dean Oliver’s theory nor the increase in the frequency of three point shots explains the increase in pace, though. So, why did the pace increase?
Image 2 shows the variation in the field goal conversion percentages with the change in time remaining on the clock. Clearly, shots taken early in the possession have a higher conversion rate. This is mostly because of the inability of defenses to get back to their defensive positions in such a short time span. This knowledge led to teams focusing more on fast breaks and transition plays. The reduction in time per possession explains the increase in the number of possessions per game (or pace) as well.
Shot conversion rates
This change in pace of the game should have directly increased the field goal conversion rates. Let us see which range of shots has seen this increase.
Image 3 reveals that the NBA players have not gotten better at making shots. The increased points per possession should be solely explained by the three point revolution, then. Image 4 confirms that.
As you can see, the yellow color of the mid range shots has been constantly decreasing and the three pointers have replaced those shots.
Free Throws
Remember, our discussion on points per possession has not covered free throws. Intuitively, one would believe that the increase in three point attempts would lead to reduced contact between players and therefore, fewer players would be fouled in the offensive half. This may have offset some or all of the increase in field goal points. Let us see if that is the case.
Image 5 confirms our hypothesis. Careful examination of the orange line which represents free throw attempts per 100 possessions shows that free throw attempts have seen two significant drops in the past decade. The first drop is approximately worth 2 free throws and coincides perfectly with the beginning of the three point revolution in 2012. The second drop of 1.7 free throw attempts per 100 possessions came in the previous completed season. I checked the corresponding numbers for this season and found that half the deficit has been recovered this season. This recovery might well be attributed to the new ‘freedom of movement’ related rule changes introduced in the NBA this season.
To see if the reduction in free throw points has offset the increase in points per 100 possessions (which, remember, did not include free throws), let us create another metric which adds them up. I call it total points per 100 possessions. We’ll compare total points per possession for two 7-year periods, 2004–2011 2011–2018.
Image 6 shows that the field goal points have increased by 2.51 points per 100 possessions and free throw points have decreased by 2.49 points per 100 possessions. Contrary to popular belief, this chart shows that the three-point revolution hasn’t increased point scoring at the NBA. This doesn’t seem right. If it were not beneficial, so many analytics heavy teams would not be focusing on the three point shots. Surely, there is something more to it that we are missing.
A deeper look at image 4 shows that the proportion of three point shots had another major increase in the 2016-17 season. In the 2015–16 NBA season, 28.3% of all shots were 3-pointers. This figure rose to 31.4% in 2016–17 and 33.5% in 2017–18. Reproducing image 6 for the previous two seasons answers the mystery:
The points earned on free throws have gone done by 0.5 while the field goal points have increased by more than 3.3 points per 100 possessions. The total points per 100 possessions has increased to almost 108. This could be because not all teams took to the three-point revolution immediately. Most teams joined the three-point bandwagon in the last couple of years which has led to the increased numbers that we are now seeing.
Rebounds
With the increased focus on three point shots which have a slightly lower conversion rate, we should expect more rebounding opportunities. Image 7 explores that dimension of the game.
The three-point revolution has contributed to a very slight increase of almost 0.5 rebounds per 100 possessions. The decreasing height of the blue bar is telling, though. The offensive rebounding rate has been consistently decreasing. This should be explained by the fact that the offensive players are farther from the rim. This is confirmed by another statistic; Offensive rebounds as a proportion of total rebounds have a direct negative correlation (-0.91) with the proportion of three point field goal attempts.
Turnovers
I don’t expect a change in the turnover counts because of the three-point revolution. The increased pace of play might have an impact, though. In the quest to play faster, offenses might make more mistakes which could manifest itself in turnover counts. On the contrary, turnover rates might be directly correlated with the length of a possession. Therefore, lesser time might also mean fewer turnovers. Image 8 shows that the second theory plays itself out. Turnover rates have gone down almost every year since 2012.
Turnover rates have a strong negative correlation (-0.76) with pace which gives more substance to the theory layed out above.
Conclusion
The heavily touted three-point revolution more has led to a decrease in free throws, an increase in defensive rebounds and a decrease in offensive rebounds. The cumulative effect of these changes has increased the shooting efficiency of the teams. Another significant change in the ‘new NBA’ is the increase in the pace. It has led to increased turnovers. For success in the ‘new NBA’, the key differentiation is the adaptability to an increased pace and being better than the rest of the pack at one or more of the ‘four factors’ (effective field goal percentage, rebounding, turnovers or free throws), both offensively as well as defensively. Being good at three-pointers alone might not be enough.
Click here for part 2 of this series where I explain the evolution of the role of different player positions in the NBA.
Data courtesy stats.nba.com. All statistics are for the regular season only.
Penned by Vibhor Agarwal — Graduate Student, Sports Management at Columbia University
